Curculio nucum

Pictures :  Egg        Larva       Pupae        Male      Female    Damage  Mating             Damage on husk     Adult feeding     Adult on husk

Description

Adults 7-8 mm long, entirely greyish red and covered with  a strong pubescence. Rostrum slender, strongly curved, longer than the body in the female, shorter in male. Larvae is 15 mm   long, apodous, thick, curved, creamy white, head is brown.

Biology and Damage

C.nucum overwinters as a full grown diapausing larvae in the    soil underneath the infested trees. After late march overwintering larvae starts to pupate and adults are seen. Adults emergence reach peak in early May. The adults can live up to 3 months.  Young adults feed on the flowers, opening buds and young foliage, altough this damage is not serious. Mating and  oviposition begin in June and goes on during July. Females    make a small wound on the nut shell by their beak and generally deposit one egg per each nut. Each female can produce about    40 eggs.  Embriyonic development lasts 8-10 days. After egg hatching , the larvae penetrates to the kernel and feed on it and completes development in 4-5 weeks. Fully grown larvae chew their way out of the nut on one of the sides. The holes on the    nuts are 1.5-2 mm in diameter. The larvae come out of the nut ,     go into soil, form a hard silken coccoon amongst the roots of hostplant, at a depth of 10-15 cm and overwinters until the following spring. Some overwintering larvae may stay in diapause 2-3 years. There is only one generation per year.  In Turkey , the orchards at slightly higher altitudes are more  likely to have B. nucum infestations than those that are planted at lower elevations. Most of the thin-shelled nut varieties appear to be more susceptible than the thick- shelled varieties.

Altough this pest feed on leaves, flowers and opening buds ,     this damage is not important. But as the season progresses     they start to feed on small nut and cause empty nuts that are brown in color and premature nut drop. After egg hatching,  the larvae feed on kernel inside of nut and cause empty,black    and holed nuts. These nuts drop the ground.

Common Names

DE: Haselnussbohrer, Nussrüssler, S: Gorgojo del avellano,      FR: Balanin des noisettes, IT: Balanino delle nocciole,  GB: Nut weevil , TR: Findik Kurdu